Codominance and Incomplete Dominance
Country: United States
Date: February 2007
What is the easiest way to teach students the
difference between codominance and incomplete dominance? They
always confuse them.
Codominance - A form of inheritance in which both alleles
are equally shown.
Blood typing is a great example.
AB blood is the codominant relationship between the A protein and B
protein both expressing themselves completely.
AO (type O allele means there is no protein), A is dominant and you
see type A phenotype.
BO is the same except you see the B phenotype. Type O is recessive.
Incomplete dominance - A form of inheritance in which the
heterozygous alleles are both expressed,
resulting in a combined phenotype.
The one example that most books
give is seen in some flower colors.
A red and a white allele gives pink. If it were codominance, you
would see the red and white colors.
Incomplete dominance is most commonly found in plants.
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Update: June 2012